OCTOMERIS ANGULOSA. _G. B. Sowerby._ Zoological Journal, vol. 2,
July, 1825. And Genera of Recent and Fossil Shells, Plate.
---- STUTCHBURII. _J. E. Gray._ Annals of Philosophy, new series,
vol. 10, August, 1825.
---- AUGUBRA (?) _Chenu._ Illust. Conch., Tab. 4, fig. 2.
_Shell dirty white, rugged and massive: alæ thick, with their sutural
edges coarsely crenated._
_Hab._--Algoa Bay, Cape of Good Hope. Attached to littoral rocks;
often associated with _Balanus Capensis_ and _Chthamalus dentatus_;
Mus. Brit., Cuming, Stutchbury, Bowerbank.
_General Appearance and Structure of Shell._--Shell extremely rugged,
irregular, massive, generally much corroded, steeply conical or even
sub-cylindrical: orifice large, broad, rhomboidal, of nearly equal
breadth at both ends. Colour dirty white, often slightly tinted
yellow from the investing membrane, and from thin layers of punctured
membrane alternating with the laminæ of shell. The parietes, in old
specimens, have very irregular longitudinal ridges, or rather plates
projecting out, sometimes much branched, and generally curved inwards
so as to meet each other, thus forming round the basal margin a
circle of cylindrical apertures. In old large specimens the radii are
not developed, and till the compartments are disarticulated there
is no trace of the toothed structure of their sutural edges: in
this condition the sutures exist as deep, rugged, narrow fissures.
In younger shells, the radii, though narrow, are distinct, and have
their surfaces transversely ribbed, and their edges toothed and
interlocked with the teeth of the recipient furrow. Some of the
specimens present a curiously deceptive resemblance to _Elminius
plicatus_. Basal diameter of largest specimen, one inch and a
quarter; height one inch.
The parietes are remarkably thick, but the compartments separate
easily: I have, however, seen one instance in which they were
partially calcified together. Their internal surfaces are
very smooth. The sheath does not descend low. The alæ project
rectangularly; they have thick edges, and these are coarsely crenated
in transverse lines. Of the radii sufficient has been said.
_Scuta_ (fig. 2 _b_): these, in all the specimens seen by me but
one, have been deeply corroded, and their outline, as in Chthamalus,
considerably modified: in the one specimen well preserved, the
exterior growth-ridges were extremely prominent. The articular ridge
does not project much, nor is the articular furrow very deep. There
are more or less distinct crests for the lateral depressor muscles.
The _Terga_ are rather narrow, with a small rounded spur, moderately
distinct. The tips of the crests for the depressor muscle barely
depend beneath the basal margin.
_Mouth_: labrum considerably bullate, with the crest hairy and
furnished with a few most minute teeth. Palpi small, with their
tips not nearly touching each other. Mandibles with four teeth,
of which the lower ones are laterally double: inferior pectinated
portion small. The maxillæ are notched, but their outline differed on
opposite sides of the individual examined. Outer maxillæ bilobed on
their inner face.
_Cirri._--The first pair has the rami unequal in length by about
three segments, having six segments on one and nine on the other
ramus. In the second pair the anterior ramus is remarkably short and
extremely broad; the five segments of which it is composed being
thickly covered with bristles, some of which are very coarsely and
doubly pectinated: the posterior ramus is nearly twice as long as
the anterior ramus, and has eleven segments; of these, excepting the
two basal segments which are rather thickly covered with spines, the
others resemble in the arrangement of their spines the four posterior
pairs of cirri, with the exception that there is a single transverse
row of rather long spines along the upper and inner lateral edge
of each segment. The segments in all the four posterior pairs of
cirri resemble each other in bearing each four pairs of main spines
(of which the two lower pairs are short), with a tuft of small
intermediate spines.
The penis is remarkable from its very small size and shortness, not
being more than once and a half as long as the pedicel of the sixth
cirrus.